Late Cretaceous Sedimentary Environments And Mass Burying Of Shantungosaurus (Hadrosauridae) In Zhucheng Region, Shandong Province

Zhucheng City of Shandong Province is one of classic areas for the study on Cretaceous strata and fossils in China, yielding rich Late Cretaceous hadrosaurid dinosaurs famously.This paper gives a brief historical review of the study on the duckbilled dinosaur Shantungosaurus giganteus Hu, 1973, from the Xingezhuang Formation of early Late Cretaceous age at longgujian valley of Kugou village, Lübiao Town, Zhucheng City and makes a discussion on the systematical relationship between Shantungosaurus giganteus Hu, 1973 and Zhuchengosaurus gigantus Zhao et al., 2007. On the basis of the burial characters, skeletal structures and ontogenic characteristics, Zhuchengosaurus maximus Zhao et al., 2007 is considered to be synonymic with Shantungosaurus giganteus Hu, 1973. According to the naming priority in palaeontology, Zhuchengosaurus maximus Zhao et al., 2007 is regarded to be invalid herein. This paper also deals with the lif behaviour and environment of Shantungosaurus giganteus which is thought to be a terraneous, gregarious, maigre (or plant-eating) duckbilled dinosaur, living in hills and intervales with warm weather, plentiful rainwater and flourishing vegetation.The Cretaceous strata in Zhucheng basin are composed of 9 formations of 2 groups. The Qingshan Group (Lower Cretaceous) can be subdivided into 5 formations (in ascending order): the Qugezhuang formation, the Shuimutou Formation, the Doushan Formation, the Xiaoheigou Formation and the Tianjialou Formation, yielding rich fossils such as psittacosaurid dinosaurs. The Wangshi Group (Upper Cretaceous) can be subdivided into 4 formations (in ascending order): the Xingezhuang Formation, the Jiangjunding Formation, the Jingangkou Formation and the Changwanpu Formation. Among them, the Xingezhuang Formation contains a dinosaur fauna characterized by yielding lots of Shantungosaurus giganteus, and both the Jiangjunding Formation and the Jingangkou Formation contain a dinosaur fauna marked by yielding Tanius and Tsintaosaurus.Based upon detailed studies of lithofacies and sedimentology, a fluvial fan-braided channel model has been developed for the restoration of Cretaceous depositional environments in Zhucheng area, eastern Shandong. Using this model, major taphonomic modes have been recognized for the explanation of the exceptionally mass occurrence of hadrosaurid dinosaur remains found in Zhucheng area. The first one (T-DF) is for the mud-flow deposits with sandy and muddy conglomerates; the second one (T-FP) is for the floodplain deposits with immature paleo-soils, shales and mudstones intercalated with braided conglomerates; the third one (T-BRC) is for the sandy and muddy conglomerates with inclined bedding. The three major taphonomic modes are dominantly associated with mudflow and floodplain deposits, indicating the preferential preservation of vertebrate materials in these microfacies and the exceptionally mass death of hadrosaurid dinosaurs caused by sudden events such as mud-rock flow or outbreak of mountain torrents, rather than by the K/T event.